The present invention relates to a microphone and a microphone housing. Background Art
As illustrated in FIG. 14, among microphones 100, for example, unidirectional condenser microphones, there is one in which a circuit board 160 that configures an electronic circuit is arranged in proximity to the rear of a diaphragm of a microphone unit 110. Further, the unidirectional condenser microphone takes in sounds from two directions from the front and the rear of the diaphragm in order to realize unidirectionality. Therefore, a front cover 130 in front of a housing 120 includes a front opening portion 131. Further, as illustrated in FIG. 15, the housing 120 that houses the microphone unit 110 of the unidirectional condenser microphone includes a rear opening portion 121 in its side surface.
The circuit board in which an impedance converter is mounted is installed near the rear opening portion 121 in the side surface of the housing 120. Therefore, in the microphone 100, when a high-frequency current comes in from a vicinity of the rear opening portion 121, the impedance converter detects the high-frequency current, and noises occur. To suppress the noises, a shielding member 150 made of a metal mesh or a punching metal cut in a strip manner is provided in the rear opening portion 121, and configures electrostatic shielding.
An opening area of the rear opening portion 121 of the housing 120 is required to be large to efficiently take in the sounds. Further, if the opening area of the rear opening portion 121 is large, external electromagnetic waves are easily mixed. Therefore, the shielding member is required to be attached in a reliable manner.
As illustrated in FIG. 16, conventionally, the shielding member 150 has a cylindrical shape, and is housed inside the housing 120 along the side surface of the housing 120 and is fixed with an adhesive or the like. However, the shielding member 150 is sometimes shifted from an original fixing position because sufficient stress is not applied when the shielding member 150 is fixed inside the housing 120. In this case, the shielding member 150 cannot reliably cover the rear opening portion 121 inside the housing 120, and cannot obtain high electrostatic shielding performance. Further, to obtain the high electrostatic shielding performance, the shielding member 150 is required to be grounded with a short conductive path.
JP 4939922 B discloses a capacitance microphone provided with a coil spring that presses a metal mesh against an inner wall surface of a unit case in order to perform electromagnetic shield in a rear acoustic terminal of the microphone.
JP 5449932 B discloses a capacitance microphone in which a plurality of openings that allows sound waves to pass through is formed in a shielding plate of the microphone.
The technologies disclosed in JP 4939922 B and JP 5449932 B cannot make a ground path of a shielding member short because the shielding member may be fixed while remaining shifted. Therefore, it is difficult to obtain the high electrostatic shielding performance with the technologies disclosed in these patent documents. In addition, the technology disclosed in JP 4939922 B requires the coil spring that presses the metal mesh, and thus the configuration becomes complicated.